Does a case-insensitive comparison of two 7-bit ASCII strings.
    Format
      #include  <strings.h>
      int strcasecmp  (const char *s1, const char *s2);
1 – Arguments
 s1
    The first of two strings to compare.
 s2
    The second of two strings to compare.
2 – Description
    The strcasecmp function is case-insensitive. The returned
    lexicographic difference reflects a conversion to lowercase.
    The strcasecmp function works for 7-bit ASCII compares only. Do
    not use this function for internationalized applications.
3 – Return Value
    n                  An integer value greater than, equal to, or
                       less than 0 (zero), depending on whether the
                       s1 string is greater than, equal to, or less
                       than the s2 string.